Reciprocating high-pressure pumps, such as those for oil field use, are usually designed in two sections, the (proximal) power section (herein “power end”) and the (distal) fluid section (herein “fluid end”). The power end comprises a crankshaft, reduction gears, bearings, connecting rods, crossheads, crosshead extension rods, etc. The fluid end comprises a housing which in turn comprises one or more functional units, each functional unit comprising a suction valve, a discharge valve, and a plunger or piston bore in which a reciprocating plunger or piston alternately produces suction strokes and pressure strokes. See, e.g., U.S. Pat. No. 7,513,759 B1, incorporated by reference.
Suction valves of high pressure oil field pumps experience wide pressure variations between a suction stroke, when the valve opens, and a pressure stroke, when the valve closes. For example, during a pressure stroke a valve body may be driven toward contact with its corresponding valve seat with total valve closing force that may vary from about 50,000 to over 150,000 pounds (depending on pumped fluid pressure and valve body area); the closing force is applied longitudinally to the proximal surface of the valve body. Actual valve closure impact occurs with metal-to-metal contact between the valve body's valve seat interface and the valve seat itself.
Valve closure impact is particularly prominent when a conventionally-stiff valve body contacts a conventional frusto-conical valve seat. The valve body's longitudinal movement typically stops abruptly, together with the associated longitudinal movement of a proximal mass of pressurized fluid in contact with the valve body. The kinetic energy of the moving valve body and pressurized fluid is thus nearly instantly converted to a high-amplitude closing energy impulse of short duration.
A portion of the sharply rising impulse of closing energy is quickly transmitted via the valve seat to adjacent areas of the pump housing in the form of characteristically broadband vibration. And this broadband vibration then induces damaging resonances within the valve as well as within adjacent pump housing structures. See, e.g., U.S. Pat. No. 5,979,242, incorporated by reference. Both rapid valve wear and the early emergence of structurally significant fatigue cracks in the pump housing near the valve seat are commonly seen under these conditions.
Proposed designs valve designs in the past have included relatively lighter valve bodies comprising one or a plurality of interior cavities. See, e.g., U.S. Pat. No. 7,222,837 B1, incorporated by reference, and referred to hereinafter as the '837 patent. Notwithstanding the somewhat lower closing energy impulse amplitudes theoretically associated with such lighter valve bodies, they nevertheless have not found wide industry acceptance. A more effective valve design for reducing pump damage due to closing energy impulse-related vibration is thus needed.